Homo- and copolymerization of vinyl monomers using tautomeric aldehyde derivatives as catalysts



United States Patent Germany No Drawing. Filed Nov. 10, 1964, Ser. No. 410,280 Claims priority, application Germany, Nov. 14, 1963, D 42 932 Claims. 01. 260-895) The present invention relates to an improved process for the homoor copolymerization of vinyl monomers.

It is known that vinyl monomers can be polymerized in bulk with radical forming catalysts. Such polymerized vinyl compounds are of great interest for the production of organic glasses. One disadvantage in the known polymerization processes resides in the fact that the bulk polymerization can only be caused to progress uniformly with great difliculty and usually tends to an uncontrolled progress of the polymerization which greatly reduces the quality of the organic glasses obtained. In order that the polymerization could be controlled to some extent only very small quantities of radical forming catalysts were employed. The quantities were so small that the time required for the polymerization was very long, and for many technical applications too long.

An object of the invention is to provide for a polymerization of vinyl monomers which proceeds rapidly under daylight or exclusion of light but which is controllable during every moment thereof so that clear and many technical applications too long.

According to the invention it was found that bubble and streak free products could be obtained when the homoor copolymerization of vinyl monomers is carried out in the presence of tautomeric compounds of the formulae:

in which:

R=hydrogen, alkyl of 1-3 carbon atoms or halogen R'=hydrogen, alkyl of 1-3 carbon atoms, phenyl, nitrile or COOR in which R =alkyl of 1-3 carbon atoms.

Such tautomeric compounds can be used singly or in admixture.

Esters and amides of acrylic or methacrylic acid and especially methyl methacrylate above all come into consideration as the vinyl monomers to be polymerized according to the invention. However, rapid and controllable polymerization of other vinyl monomers, such as, for example, acrylonitrile, vinyl carbazole, vinylpyrolidone, vinyl chloride, vinylidene chloride and styrene can also be effected with the catalysts according to the invention.

Suitable catalysts according to the invention, for instance are: (=1) phenyl acetaldehyde, p-tolylacetaldehyde, p-chlorophenylacetaldehyde, diphenylacetaldehyde, hydratropaldehyde in which the aldol-enol equilibrium strongly favors the aldol form; (2) phenylformyl acetic acid methyl ester (in a and [3 form), phenylformyl acetic acid nitrile, preferably in enol form. 0f the above named compounds, hydratropaldehyde [C H CH(CH )CHO] and phenylformyl acetic acid nitrile have proved partic ularly suited. Both of such compounds in addition to exhibiting a strong catalytic activity, also possess great sta bility against autopolymerization and oxidation.

The quantities of the catalysts employed according to the invention can be varied within wide limits and he between 0.001 and 10% by weight with reference to the vinyl monomer to be polymerized. It is surprising that catalyst quantities of 10% by weight do not lead to an explosive course of polymerization as is the case with peroxide and azo compound catalysts.

In addition, the catalysts employed according to the invention can be used at practically any desired temperature, even higher temperatures. The polymerization temperatures do not depend upon the polymerization catalyst as is the case with peroxidic and azo catalysts, which decompose at higher temperatures, but are governed by the particular vinyl monomer concerned. The polymerization time therefore can be shortened by the use of elevated temperatures.

It was furthermore found that the polymerization initiating action of the catalysts according to the invention could be increased substantially by irradiation with UV light but that, on the other hand, room light or exclusion of light has little influence. Nevertheless, the catalysts according to the invention have the advantage over pure photosensitizers that even under the exclusion of light a polymerization accelerating effect is attained which leads to good polymerization yields. This effect is favored by a slight increase in temperature to, for example, C.

The presence of oxygen has different influences on the catalytic effect achieved, depending upon whether the catalyst is present in aldo or enol form. Whereas the catalyst eifect of the aldo form is increased by the exclusion of oxygen, traces of oxygen had to be present if the enol form is to have its maximum polymerization initiating action.

It is also of interest that the degree of purity of the vinyl monomers to be polymerized is of influence on the catalytic effectiveness of the catalysts according to the invention. It was found that the conversions with usual commercial, stabilized vinyl monomers with the catalysts according to the invention, whether in aldo or in enol form, were higher than with freshly distilled monomers. It is possible therefore to polymerize commercial vinyl monomers directly with the catalysts according to the invention without the necessity of first subjecting them to a time consuming distillation.

The catalysts according to the invention are preferably used in bulk polymerization but they also can be used in solution, precipitation, emulsion or suspension polymerizations.

The catalysts according to the invention are suited for homo and copolymerization of vinyl monomers and therefore the vinyl monomers can either be polymerized with themselves or copolymerized with other vinyl monomers. The polymerizations concerned herein therefore only involve vinyl monomers as the polymerizable component or components and do not concern, for example, copolymerization of vinyl monomers with unsaturated polyester resins. The term vinyl monomers is employed herein to signify monomers which undergo vinyl polymenization and contain a terminal CH =C= group.

The catalysts employed according to the invention can also be used in combination with the usual catalysts, such H as, peroxides or azo compounds. Naturally the latter can only be employed in very small quantities in order to avoid an explosive course of reaction. For example, the addition of only 0.05% by weight of azo diisobutyryl dinitrile to 0.5% by weight of hydratropaldehyde in a polymerization of methyl methacrylate at 70 C. under nitrogen increases the conversion obtained from 2% by Weight per hour to 12.5% by weight per hour. Good control over the progress of the polymerization can still be maintained with such small additions of azo compounds.

Infra red spectra of polymethyl methacrylate which had been polymerized at 80 C. in bulk with 0.5% by weight of hydratropaldehyde or phenylformyl acetic acid nitrile with reference to the starting monomer indicates that the polymethacrylates obtained were atactic. They are equal to those obtained at higher temperatures with radical forming catalysts, such as benzoyl peroxide. The molecular weights, determined in the Ostwald-viscosimeter (capillary 0.4 mm.) at 20 C. in benzene were 2.5 to 3.5 million as contrasted to molecular Weights around 1.3 million in polymethyl methacrylate polymerized with benzoyl peroxide.

The following examples will serve to illustrate the invention with reference to several embodiments thereof. In such examples the proportions are given by weight unless otherwise specified.

Example 1 20 g. samples of methyl methacrylate which had been distilled in a silver plated high vacuum insulated distillation column 50 cm. high at about 50 C. under vacuum were each weighed into a reaction vessel with 0.5 of the catalysts given in the following Table 1. Subsequently the reaction vessel which was provided with a reflux condenser was rinsed 5 minutes with 99.999% nitrogen and then dipped into a thermostatically controlled jacket provided with a sealing liquid which maintained the polymerization temperature constant to 0.1 C. About every minutes a small sample was pipetted out of the methyl methacrylate solution, which was maintained homogeneous by a magnetic stirrer, and such sample cooled to C. and the refractive index determined at 20 C. This method permitted conversions up to about 10 to 12% to be determined. With higher conversions homogeneous distribution could not be maintained in the polymerization vessel even with the aid of a magnetic stirrer. During the entire polymerization period a slight superatmospheric pressure was maintained in the system so that no air could enter. The results showed good reproducibility.

The refractive indices were exactly determined to four places With a Zeiss-Abbe-Refractometer Model A which was thermostatted to 20 C. by a Colora-Ultra-thermostat type K. The calculation of the conversion to polymethyl methacrylate from the refractive index n was according to the formula employed by V. W. Smith (J. Amer. Chem. Soc., 68, 2059 (1946)), namely:

Percent polymethyl methacrylate: 1.22 X 10 X 1311 wherein A =the difference between the refractive index of the monomer solution (inclusive of catalyst) and the refractive index of the monomer polymer solution after a certain polymerization period.

Example 2 Tests were carried out analogously to those of Example 1, however, with the difference that only hydratropaldehyde was used as the catalyst in varying quantities. The polymerization temperature was 80 C.

The following table gives the conversions attained:

TABLE 2 Catalyst quan- Conversion, Polymerization tity, percent percent time, minutes *Almost.

The quantity of catalyst employed is with reference to the quantity of vinyl monomer concerned.

Example 3 Tests again were carried out analogously to Example 1, however, with the difference that it was only carried out with 1.0% of hydratropaldehyde as catalyst and that they were carried out at temperatures varying from 40 to 90 C.

The influence of UV light on the velocity of polymerization was investigated in the following manner:

10 g. samples of freshly distilled methyl methacrylate and the corresponding amount of catalyst were each weighed into a polymerization vessel. Thereupon the polymerization vessel was provided with a wide reflux condenser and a UV lamp and then rinsed with nitrogen for 5 minutes and dipped into a thermostatically controlled jacket provided with a sealing liquid. The catalysed samples were polymerized for one hour at C. with constant stirring with a magnetic stirrer and constant passage of nitrogen. Some of the samples were polymerized while being irradiated with a 70 watt high pressure mercury vapor lamp at a distance of 40 cm. and in comparison some of the samples were polymerized without such 60 irradiation.

TABLE 1 Catalysts Catalysts Percent Poly- Percent Poly- RC6H4CH-CHO MMA C5H5-CHCHO MMA R B. after 1 hr. R after 1 hr. R at C. R at 80 C.

0.5% Aldotorm 0.5% Enoltorm Phenylacetaldehyde H H 6. 2 Phenylformylacetic acid nitrile -CN 6. 4 Hydratropeldchyde H CH3 4. 7 Ihenyltormylacetic acid C O O CH; 2. 4

methylester (u-iorm). Diphenylacetaldehyde -H 'CGH5 2. 2 Phenyltormylacetie acid C O 0 CH1 9. 6

methylester (B-Iorm). p-Tolyl acetaldehyde CII3 H 7. 4 p-Chloro-phenylacetaldehyde. C1 -11 6.0 Control without catalyst 0. 1

The results obtained are given in the following table:-

TABLE 4 Polym. Wt. Percent Poly-MMA Catalysts Formula time, nun.

Daylight UV light Hydratropaldehyde -Q C5135-CH-CHO 60 4.6 11. 5

Phenylformylacetic acid nitrile CnH5-CH-CHO 60 4. 2 6. 1

Diacetyl" ,CH CO-COCH 60 3.8 14.4 Benzoin C@H --C|lHCO-OH 45 2.6 17.8

Control without catalyst 60 1. 1

*As comparison.

Example Example 6 In order to ascertain the influence of daylight and exclusion of light, 10 g. samples of methyl methacrylate were each polymerized at 80 C. with 0.5% of the catalysts indicated in the following table in ampoules which had been sealed olf with 99.999% nitrogen. The polymerization time was 1 hour. Exclusion of light was eilected by enclosing the ampoules in aluminum foil.

TABLE 5 In order to investigate the influence of oxygen, three difi'erent types of polymerization were carried out in ampoules. According to method A, the polymerization was carried out in open ampoules provided with reflux condensers, according to method B, the polymerization was carried out in ampoules which had been sealed under 99.999% nitrogen and according to method C, the polymerization was carried out in ampoules which had been rinsed with 99.999% nitrogen, subsequently frozen in a Dry Ice-acetone mixture and evacuated under high vacuum. In method C, after melting under nitrogen the proggfi gg m cednre was repeated three times and finally the ampoules Catalysts, each 0.5 wt. percent sealed under high vacuum and polymerized. In all in- Daylight Light stances the starting temperature for the polymerization excluded was 0 C. After completion of the polymerization the ampoule content in each case was quenched in ice water llgilydratfropaldehyga. dn tfii 5.3 and the conversion determined refractometrically as in 1'11 g fgg g gi'f g gg 27 L6 40 Example 1. The capacity of the ampoules was 20 cc. and Benzoin as comparison photosensitizeruu the amount of methyl methacrylate introduced was 10 g.

The results are given in the following table:

TABLE 6 Wt. percent polymethyl methacrylate Catalyst Wt. percent Polyrn. time, Polym. temp., MMA, fresh min. C. distilled, g.

A B C Hydratropaldehyde, 100% Aldoform o. 5 60 80 10 4. 5 5. 6 6. 5 Phenylformylacetic acid nitrile,

100% Enolform 0. 5 60 80 10 1. 8 8.0 2.1

Example 7 Tests were carried out exactly as in Example 6 except that technical stabilized methyl methacrylate was used instead of freshly distilled methyl methacrylate.

The results obtained are given in the following table:

TABLE 7 Wt. percent polymethyl methacrylate Catalyst Wt. percent Polym. time, Polym. temp., MMA, techn. min. C. stabilized, g.

A B C Hydratropaldehyde, 100% Aldoform o. 5 10 0. 2 10. 4 15. 6 Phenylformylacetic acid nittile,

% Enolform 0. 5 60 80 10 5. 6 11.3 2.9

Example 8 following Table 9. The polymerizations were carried Out in solution under polymerization condition (b) described t The polymerization initiatmg ac 1011 of hydra ropalde m Example 8.

hyde on the bulk polymerization of other than vinyl TABLE 9 Monomers G. Solvent G. Polymer. Yield, wt. Polymer. time, hrs. percent M.P., 0.

Methyl acrylate l5 Ethyl acetate 10 2 59.9 96 Ethyl acrylate 5 -.-d- 10 2 59.1 Methyl methacrylate. 5 l0 4 20. 2 184 Cyclohexyl methacrylate" 6 4 44. 3 152 COPOLYMER Styrene 2.5

plus Acetone 10 2 16. 0 230 Maleic acid anhydride 2. 5

monomers than methyl rnethacrylate is shown in the following Table 8. The polymerization was either carried out in ampoules which had been rinsed out with nitrogen The conversions indicated in Tables 8 and 9 were and evacuated under high vacuum (polymerization condetermined gravirnetrically after precipitation with methdition (21)) or in ampoules which had been scaled under anol 0r ligroin. vacuum (polymerization condition (b) The melting point temperatures given were ascertained on a Kofler heating bench.

TABLE 8 Conversion, wt. percent Hydratrop- Polym. Polym. Polymer Polym. Monomers G. aldehyde, temp., 0. time, hr M.P., 0. conditions wt. percent With Without catalyst catalyst 10 1 15 13.1 1 7 134 (a) 10 1 15 100 1 7 (a) 10 1 70 15 36.2 0 (a) 10 l 120 15 57.9 0 156 (a) 16.3 0 5 80 20 14.5 0 (b) 10 1 60 15 15.1 6 0 190 (b) Vinylacetate 10 1 100 18 19.7 1 7 (b) n-Butyl acrylatem 10 0 5 80 V; 7.9 0 (b) Methyl methacryla 10 0 5 80 2 13.6 0 180 (b) Ethyl methacrylate- 10 0 5 80 2 1.8 0 9 (b) n-Butylmethaciylatc.. l 10 0 5 80 2 31.3 0 (b) COPOLYMERS Methyl methacrylate 5 plus 0.5 80 2 9.9 1 160 (b) Acrylonitrile 5 Styrene 5 plus Acrylonitrile 2. 5 U. 5 80 2 G. 4 154 (b) p us Vinylcarbazole 2. 5 Styrene 3.3

plus Methyl methacrylate 3. 3 0- 5 S0 2 2. 5 144 (b) p ns Vinylideue chloride 3. 3

Example 9 The polymerization initiating action of 1% of hydratropaldehyde upon the homopolymerization and copolymerization of various vinyl monomers is shown in the 75 9 10 Example 10 in which R is selected from the group consisting of hydrogen, alkyl of 1-3 carbon atoms and halogen, R is Polymerizations were carried out as precipitation polymerizations under the same conditions as in Example 9. Selected from the group conslstmg of hydrogen alkyl of The results are given in the following table:

TABLE 10 Conversion percent Polym. Polym. Monomers G. Preclpitant G. Temp., time, hrs.

With Without catalyst catalyst Methyl methaerylate 6 Cyclohexane 10 8O 30.1 0 Acrylamide 5 th 01 80 1 59.8 16.3 Methacrylamide- 5 10 80 55. 6 39. 0 Acrylic acid 5 10 80 2 64. 2 0

GOPOLYMER Styrene 2.5

plus Cyclohexeno 10 80 2 14. 2 Maleic acid anhydride 2. 6

Example 11 l-3 carbon atoms, phenyl, nitrile and COOR wherein 5 R is alkyl of 13 carbon atoms.

2. The process of claim 1 in which the quantity of tautomeric compound is 0.001 to 10% by weight with Suspension polymerizations were carried out under the conditions of Example 9. The results are given in the following table:

TABLE 11.SUSPENSION POLYMERIZATION OF METHYL METHACRYLATE Monomer phase Aqueous phase Polym. Polyrn. Conversion,

temp., C. time min. percent Meth lmethac late, 10g Water, g fiydrgtropaldeg de, 0.1 g Polyvinyl alcohol, 0.5 g so 170 2 The conversions indicated in Tables 10 and 11 were reference to the monomer to be polymerized. determined gravimetrically after filtering oil and drying 40 3. The process of claim 1 in which said tautomeric the precipitated polymer. compound is hydratropaldehyde.

We claim: 4. The process of claim 1 in which said tautomeric 1. In a process for the polymerization of at least one compound is phenylformyl acetic acid methyl ester. vinyl monomer having a terminal CH =C group, the 5. The process of claim 1 in which said monomer is step of carrying out such polymerization in contact with methyl methacrylate. a catalytically effective amount of at least one tautomeric compound of the formulae: N references cited.

OH JOSEPH L. SCHOFER, Primary Examiner.

R R H. W. WONG, Assistant Examiner. 

1. IN A PROCESS FOR THE POLYMERIZATION OF AT LEAST ONE VINYL MONOMER HAVING A TERMINAL CH2=C< GROUP, THE STEP OF CARRYING OUT SUCH POLYMERIZATION IN CONTACT WITH A CATALYTICALLY EFFECTIVE AMOUNT OF AT LEAST ONE TAUTOMERIC COMPOUND OF THE FORMULAE: 